There is a trend toward recovery and reuse of pulp from used sanitary goods. Sanitary goods generally include an absorbent body, the absorbent body being composed of pulp and a superabsorbent polymer. In order to recover pulp from used sanitary goods, therefore, it is necessary to separate the pulp and the superabsorbent polymer. However, separation of superabsorbent polymers and pulp that have swelled by absorption of water is not easy to accomplish. Separation is carried out by treatment with water-soluble calcium compounds such as hydrated lime, calcined lime and calcium chloride, separating out the superabsorbent polymer by dehydration, sedimentation, dry sorting (for example, air sorting) and sifting. (Patent Literature 1, Patent Literature 2).
Since in the production of pulp, metals such as iron, copper or manganese in the pulp promote decomposition of oxygen-based bleaching chemicals, resulting in wasteful consumption of the oxygen-based bleaching chemicals, PTL 3 and PTL 4 disclose methods in which prior to the bleaching step, the metals are treated with an inorganic acid, organic acid or chelating agent and removed. However, these prior art documents do not focus on removal of calcium.